Some known domestic and commercial water heaters include flue paths which include downwardly extending legs. For example, in patent specification U.S. Pat. No. 6,237,544, there is a downdraft passage for flue gases. In this apparatus, the downdraft passage is intended to operate as a heat trap when the burner is not operating thereby reducing the loss of heat from the apparatus by convective flow or leakage of heated gases through the flue outlet during such quiescent or standby times. However such heat loss does nevertheless occur.
It is an object of the present invention to provide a water heater of the kind which uses burning of fuel to generate combustion products which are used to heat water and which has features to reduce heat loss from the water heater during quiescent or standby times when the burner is not operating.